Microstructural evolution and mechanical properties of a β-solidifying γ-TiAl alloy densified by spark plasma sintering. (November 2015)

• Record Type: Journal Article
• Authors: Niu, H.Z.; Su, Y.J.; Zhang, Y.S.; Zhang, D.L.; Lu, J.W.; Zhang, W.; Zhang, P.X.
• Is Part Of: Intermetallics. Volume 66(2015:Nov.)
• Page Start: 96
• Page End: 102
• Publication Date: 2015-11
• Subjects: Intermetallics (aluminides) -- Powder metallurgy (including sintering and consolidation) -- Microstructure -- Annealing -- Mechanical properties; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2015.07.003
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: This study deals with the densification of a pre-alloyed Ti–44Al–6Nb–1Mo–0.2Y–0.1B (at.%) powder by spark plasma sintering (SPS). The powder was produced by a plasma rotating electrode process (PREP), and then SPS densified at temperatures between 1200 and 1320 °C. At SPS temperatures below 1240 °C, the α2 -dominated dendritic structure in the PREP powder particles disappeared and the fully dense microstructure mainly consisting of γ and B2 grains formed during SPS, but several original powder particle boundaries (OPBs) still remained. While sintered above 1240 °C, OPBs vanished entirely and an uniform duplex microstructure emerged. Furthermore, fully-lamellar (FL) microstructure with mean colony size smaller than 20 μm was produced via β-homogenization annealing. This FL microstructure renders a good tensile elongation of 1.25% and yield strength of 665 MPa at room temperature. However, instability of α2 /γ lamellar structures was induced by final stabilization annealing, resulting in sharp reduction of both room-temperature ductility and high-temperature strength. Graphical abstract: Highlights: PREP pre-alloyed powders of β-γ TiAl were densified by SPS sintering. As-sintered microstructure was strongly depended on SPS temperature. Fine-grained FL microstructure was produced via SPS sintering and β-annealing. Unstability of the FL microstructure was found to deteriorate RT ductility.